Energy and power management becomes a critical aspect for portable electronic devices, such as including mobile phones. Indeed, with the advent of additional—highly consuming—new functionalities and the increase in the performance of those devices, there is a general trend towards an increase of the power consumption.
Considering the field of mobile communications, a recent mobile telephone typically includes two separate battery charging circuits: the conventional AC/DC battery charging circuit and, recently, a DC/DC charging circuit for allowing the charging of the battery through the well-known Universal Serial Bus (USB) interface.
FIG. 1 illustrates the general architecture of a two-ways charging circuit for charging a battery 100 of a conventional mobile telephone. A first USB charger circuit is based on a buck converter 110 including two switches SA and SB referenced 111 and 112) in addition to a first coil 113 in series with a resistance 114.
On the other side, a second charging circuit is connected to the mains and comprises second buck converter 120 including two switches SC and SC (resp. 121 and 122) in additional to a second coil 123 in series with a resistance 124.
Coils 113 and 123 are electronic components which are dedicated to remain outside of the integrated chip and, for the sake of clarity, the different “balls” of the integrated semiconductor have been represented in the figures under the reference 191-199.
The circuit of FIG. 1 shows that, when the electronic mobile is plugged on the alternative mains, then it is the buck converter 120 of the figure which achieves recharging of battery 100 as known by the skilled man.
Conversely, the buck converter 110 is being active when the USB interface is plugged so as to receiver current which can be, after conversion by the buck converter 120, used for charging battery 100.
Since mobile phones are required to achieve conventional data transfer with other peripherals, it is required that the mobile phone supply a DC voltage to the external USB connector. To achieve this, buck converter 120 is used to serve as a pump charge or a boost converter so as to perform Step Up voltage conversion so as to generate the so-called On The Go (OTG) voltage required by the peripheral connected to the USB interface.
It can thus be seen that a modern mobile phone requires two distinctive buck converter, one being particularly a buck/boost converter for providing two battery charging circuits through mains/USB and also for achieving OTG compatibility.
Such flexibility has however one drawback which results from the need of additional circuits and, above all, the use of two external coils 113 and 123 required for embodying the buck/boost converter, thus increasing the manufacturing costs of the mobile phones. Despite this drawback mobile telephone manufacturers still favour the use of buck/boost converters which offer effective voltage conversion with respect to the more traditional linear converter.
It has recently been shown that a recent mobile telephone might require the possibility to connect additional functionalities, such as the possibilities to connect devices complying with the 3V SIM interface, the 3V MMC interface or any audio amplifier.
Such additional requirement would normally result in the need to introduce an additional buck/boost converter for converting the battery voltage to the required 3V SIM interface (for instance), which would thus need an additional external coil.
It is highly desirable to provide the possibility of offering additional interface without significantly increasing the manufacturing costs of the mobile telephone.
Such is the aim of the present invention.